Trucks are primary carriers of cargo and the cargo may range from perishable foodstuffs to heavy logs for the pulping industry. For specialized cargoes, such as perishable foodstuffs, the art has provided quite specific trucks or truck trailers which enable the perishable foodstuffs to be transported relatively long distances and be contained therein for relatively long times without substantial deterioration of the foodstuffs. Similarly, trucks and truck trailers which are refrigerated have been provided by the art to allow long-distance shipment of frozen cargoes, e.g., frozen ice cream. Moving vans also constitute a specialized truck or truck trailer design which is particularly suitable for moving household effects and furniture. Similarly, but under radically different construction, the art has provided specialized trucks and truck trailers for the movement of livestock. Thus, the art has been quite successful in providing specific trucks or truck trailers for handling specialized cargo.
On the other hand, however, an entirely different set of problems have been faced in the art in attempts to provide trucks or truck trailers with such wide versatility that they may handle a variety of very different cargoes. Among these problems is the difficulty of providing an enclosure for certain cargoes while yet making the bed of the truck or trailer available for loading or unloading from all sides. Similarly, there is the problem of providing an enclosure for protecting cargo on one trip and yet have available an open bed for carrying irregularly-shaped cargo, which does not require the protection of an enclosure, on a return trip. Closely akin to the foregoing, is the desirability of providing a protective enclosure for carrying certain cargo, but with the ability to remove that enclosure and reduce the weight of the truck thus allowing a greater payload for the truck without the enclosure.
The art has suggested a number of arrangements for providing flexibility of the foregoing nature. Flatbed trucks with stake body sides and removable canvas tarpaulins represent one of the earliest and most successful approaches for providing a removable enclosure. This arrangement, however, does not protect the cargo from weather which passes through the openings between the slats of the stake sides. Tarpaulins cannot effectively seal these stake sides, since tarpaulins are difficult to so completely lash in place that they will not loosen during movement of the truck and allow weather into the cargo. Solid, removable stake sides have been proposed in the art, but these sides, made of wood or steel, produce an exceptionally heavy enclosure. These stake sides are not readily removed by one or two men and require the use of weight-lifting equipment to efficiently remove or replace the enclosure on the bed of the truck. Additionally, the mass of the steel or wooden stake sides is so great that they cannot be sufficiently rigidly interlocked to prevent shifting and swaying during truck movement, which also can correspondingly produce instability in the truck or trailer and significantly increase the difficulty of keeping the truck or trailer under accurate control.
The use of lighter weight metals, such as aluminum, can somewhat mitigate the problem with solid stake sides, but aluminum creates problems of its own. Aluminum metal is relatively soft and non-rigid, as compared to wood or steel, and normal truck movements can cause excessive wear, bending and breaking the aluminum enclosures. Similarly, points of stress and strain can cause the softer aluminum to bend or otherwise deform and result in difficulty of disassembly and subsequent assembly of the aluminum enclosure.
Efforts to use plastics as the material for construction of the stake sides have not met with substantial success. Plastics often suffer from brittle failure and are often not sufficiently rigid to sustain normal truck movements during transit without undue breaking of the plastic enclosure.